Distributed based station system and method for networking thereof and base band unit

ABSTRACT

The present invention discloses a distributed base station system as well as its networking method and base band unit. In this system, the base band unit (BBU) and RF unit (RFU) of the base station are separated, and the RFU is equipped with base band RF interfaces for interconnecting the BBU and transmitting data information, thereby forming the base station. Based on the separation of the BBU from the RFU, the BBU capacity is further divided at the same time, and every unit is also arranged independently. The BBU networking and capacity expansion may be achieved with capacity expansion interfaces and base band RF interfaces provided by BBU interface units in flexible and convenient ways.

FIELD OF THE TECHNOLOGY

The present invention relates to the base station technology, and morespecifically to a distributed base station system and a method fornetworking thereof and base band units forming the distributed basestation.

BACKGROUND OF THE INVENTION

In mobile communication systems, base stations are important componentsused for connecting User terminals to Base Station Controllers (BSC),receiving and transmitting radio signals between the User terminals andthe BSCs, thereby conducting User terminals to access wireless networksand simultaneously accomplishing information intercommunications betweenUser terminals and the BSCs. As shown in FIG. 1, a base stationincludes:

a Base Station &BSC interface unit, also called transmission unit, usedfor accomplishing interface functions between the base station and theBSC; a Main Processing & Timing unit, on the one hand, for controllingthe base station and exchanging cell and traffic data among the units inthe base station, on the other hand, for providing clock signals forother units in the base station; an uplink/downlink base band signalprocessing unit, used for processing symbol-level and chip-level digitalsignals in physical layer and communicating digital base band signalswith an Intermediate Frequency (IF) signal processing unit; the IFsignal processing unit, used for converting digital base band signals toIF signals or converting IF signals to digital base band signals; apower amplifier unit and a duplexer, used for amplifying the IF signalsfrom the IF signal processing unit or an antenna.

In the base station, the Base Station &BSC interface unit, the MainProcessing & Timing unit, and the uplink/downlink base band signalprocessing unit compose a base band part, while the IF signal processingunit, the power amplifier unit and the duplexer compose a RadioFrequency (RF) part which accomplishes conversion between digital baseband signals and IF signals, and transmits the processed RF signals. Thecomponents in FIG. 1 are all placed in one cabinet to form a completeBase Station.

In traditional base station systems, macro base stations and mini basestations are generally used. A macro base station generally has largecapacity so as to support the configuration of as many as 3 or 6sectors, and includes an indoor type and an outdoor type; while a minibase station usually has small capacity so as to only support theconfiguration of 1 to 3 sectors. The Mini base station is generallyrequired to have support capability of outdoor application, and acts asa strong complement for the macro base station networking.

The macro base station supports large capacity, and all its singleboards and modules are all placed in one cabinet, and thus the macrobase station has a large size and a heavy weight, therefore, it needs aspecial installation room or an outdoor installation base. While themini base station supports small capacity, the size thereof iscomparatively small and it supports pole installation or wallinstallation, so that the installation is easy and does not need specialinstallation space or floorage. The construction of the macro basestation and the mini base station generally used are introducedhereinafter respectively:

(1) In the macro base station, the transmission unit, the MainProcessing & Timing unit and the uplink/downlink base band signalprocessing unit forming the base band part are respectively placed ondifferent functional single boards, which are connected with one anotherby a backboard. Different single boards or modules may be addedaccording to different capacity expansion requirements; the duplexer,the power amplifier unit, the IF signal processing unit that form the RFpart are also placed on different functional single boards, which areconnected with each other by a backboard or external wirings. All theabove units are configured in one indoor or outdoor cabinet. An outdoorcabinet additionally includes such functional units as temperaturecontrol equipment, power supply, environment monitoring equipment andtransmission equipment. With all the components in large sizes, thecabinet is very large and heavy, resulting in high cost oftransportation and installation and a hard installation site selection,thereby, the network construction speed is badly affected. This kind ofstructure takes up a large space and leads to a high power consumptionand cost. When backup is required, it needs to add some single boards ormodules to achieve backup, thereby resulting in high backup cost andcomplicating backup action.

(2) In the mini base station, all the units in FIG. 1 are placed in acompact structural member module, thereby a mini base station having asmall size and an easy installation. A mini base station generallysupports configuration of 1-3 sectors. In the situation that one singlecabinet supports one sector, a plurality of mini base stations arenecessary for networking when more sectors should be supported or largecapacity configuration is needed, thereby complicating networking andmanagement of the system.

The mini base station has the shortcomings of small capacity,inconvenient capacity expansion and inflexible networking, although themini base station has such advantages as small size and easyinstallation. A plurality of cabinets of mini base stations should becombined when capacity expansion is required, and this is not in favorof wiring, protection and backup. Therefore, mini base stations are notfit for the expected applications of large capacity, furthermore, arenot in favor of expanding capacity of the base band part or the RF partrespectively due to the base band part and the RF part adoptingintegration design.

SUMMARY

A distributed base station system has advantages of reducing spaceoccupancy, deducing operational cost and improving operationalreliability of base station system according to the embodiments of theinvention.

A distributed base station system includes:

a base band unit (BBU), which includes a Main Processing & Timing unit,a base band signal processing unit, a transmission unit, and aninterface unit for providing an interface for intercommunicating datawith an external unit, intercommunicating digital base band signals withthe base band signal processing unit, and intercommunicating mastercontrol information with the Main Processing & Timing unit; wherein theinterface unit includes one or a plurality of primary base band RadioFrequency (RF) interface(s); and the interface unit being integratedwith the Main Processing & Timing unit, the base band signal processingunit and the transmission unit; and

a Radio Frequency unit (RFU) which includes a secondary base band RFinterface thereon;

wherein the primary base band RF interface of the BBU is connected withthe secondary base band RF interface of the RFU, and the BBU transmitsuplink/downlink base band data and master controller state informationwith the RFU via the primary base band RF interface and the secondarybase band RF interface.

Preferably, the primary base band RF interface and the secondary baseband RF interface both are high speed digital interfaces.

Preferably, the base station system includes a plurality of BBUs, andthe BBUs are interconnected with each other via wire cables or opticalfibers; the interface unit of each BBU includes one or a plurality ofprimary capacity expansion interface(s) for transmitting synchronousclock signals, base band information, transmission information and themaster control information among BBUs, to achieve interconnection anddata sharing among BBUs.

Preferably, the primary capacity expansion interface includes a primarycapacity expansion interface that provides an active/standby switchovercontrol signal. The interface unit further includes an identificationinterface for marking the type of the base station and the position ofthe BBU. The interface unit may further includes a Dry Contact inputinterface for expanding the input Dry Contact functions of the basestation. The BBUs include a master BBU that works in an active state.The BBUs may also include a standby BBU that works in a standby state.The RFU may be connected with any one of the plurality of BBUs.

Preferably, the BBUs include a slave BBU that works in a slave state.

Preferably, the system further includes an exchange BB cassette with aplurality of secondary capacity expansion interfaces, and each BBU isconnected with one of the secondary capacity expansion interfaces on theexchange BB cassette via the respective primary capacity expansioninterface of the BBU.

Preferably, the RFU is a radio remote unit (RRU).

Preferably, the RRU and the BBU are connected with each other viatransmission mediums.

Preferably, the RFU is a near-end RFU.

Preferably, the BBU is placed in a spare space of a standard cabinetwith a height higher than or equal to 1 U.

A method for networking a distributed base station system includes:

separating the base station system into a BBU and an RFU in dispersedarrangement, wherein the BBU includes an integration of a base bandsignal processing unit, a transmission unit, a Main Processing & Timingunit and a interface unit; the interface unit of the BBU includes aprimary base band RF interface, and the RFU includes at least onesecondary base band RF interface; and

connecting the BBU and the RFU through the primary base band RFinterface of the BBU and the secondary base band RF interface of theRFU.

Preferably, the base station system includes a plurality of BBUs, andthe interface unit of each BBU includes a primary capacity expansioninterface, and then, the method further includes: setting an operationstate of the BBU; and connecting the BBUs with each other via theprimary capacity expansion interface on the interface unit thereof.

Preferably, the base station system includes a plurality of RFUs, eachRFU includes a plurality of base band RF interfaces; and then the methodfurther includes: connecting a plurality of RFUs with each other viatheir respective secondary base band RF interfaces.

Preferably, the base station system includes two BBUs and the step ofsetting the operation state of the BBU includes: setting one of the BBUsas a master BBU that works in an active state while setting the otherBBU as a standby BBU that works in a standby state; and the step ofconnecting the BBUs to each other via the primary capacity expansioninterface includes: connecting the master BBU to the standby BBU via theprimary capacity expansion interface that provides an active/standbyswitchover control signal.

Preferably, the step of setting the operation state of BBUs includes:setting any one of the plurality of BBUs as a master BBU that works inthe active state, and setting the others as slave BBUs that work inslave states; and the step of connecting the BBUs to each other via theprimary capacity expansion interface includes: connecting the master BBUand slave BBUs via one or a plurality of primary capacity expansioninterface(s) providing no active/standby switchover control signal.

Preferably, the step of setting the operation state of the BBU includes:setting any one of the plurality of BBUs as a master BBU that works inan active state, and setting the others as slave BBUs that work in slavestates; and the step of connecting BBUs with each other via the capacityexpansion interfaces includes: connecting the master BBU with the slaveBBUs via one or a plurality of primary capacity expansion interface(s)providing the active/standby switchover control signal; and the MainProcessing & Timing unit of the master BBU shielding the active/standbyswitchover control signal.

Preferably, the step of connecting BBUs with each other via the capacityexpansion interfaces includes: connecting the master BBU with each ofthe slave BBUs via one or a plurality of primary capacity expansioninterface(s) providing active/standby switchover control signals; andthe Main Processing & Timing unit of the master BBU shielding theactive/standby switchover control signal.

Preferably, the step of setting the operation state of BBU includes:setting anyone of the a plurality of BBUs as a master BBU that works inan active state, setting another one of the plurality of BBUs as astandby BBU that works in standby state, and setting the others as slaveBBUs working in slave states, the master BBU and the standby BBU beingnot the same one; and wherein the step of connecting BBUs with eachother via the primary capacity expansion interfaces includes: connectingthe master BBU with the standby BBU via the primary capacity expansioninterface that provides the active/standby switchover control signal,and connecting the standby BBU with the slave BBU via one or a pluralityof primary capacity expansion interface(s) providing no active/standbyswitchover control signals.

Preferably, the step of setting the operation state of BBUs includes:setting any one of the plurality of BBUs as a master BBU that works inan active state, setting another one of the plurality of BBUs as astandby BBU that works in a standby state, and setting the others asslave BBUs that work in slave states, the master BBU and the standby BBUbeing not the same one; and wherein the step of connecting BBUs to eachother via the primary capacity expansion interfaces includes: connectingthe master BBU with the standby BBU via the primary capacity expansioninterface that provides the active/standby switchover control signal,and connecting the standby BBU with the slave BBU via one or a pluralityof primary capacity expansion interface(s) providing the active/standbyswitchover control signal, and the Main Processing & Timing unit in thestandby BBU shielding the active/standby switchover control signal.

Preferably, the step of connecting BBUs to each other via capacityexpansion interfaces includes: connecting the standby BBU with eachslave BBU via one or a plurality of primary capacity expansioninterface(s) providing the active/standby switchover control signal withthe Main Processing & Timing unit in the standby BBU shielding theactive/standby switchover control signal.

Preferably, the base station includes a plurality of slave BBUs, and theplurality of slave BBUs are interconnected with each other via theprimary capacity expansion interfaces, the method further including anyone step of the following steps: interconnecting slave BBUs to eachother via primary capacity expansion interfaces that provide noactive/standby switchover control signal; and interconnecting slave BBUsto each other via primary capacity expansion interfaces that provide theactive/standby switchover control signal, meanwhile shielding theactive/standby switchover control signal by the Main Processing & Timingunit of at least one of the two interconnected slave BBUs.

Preferably, the method further includes: configuring an exchange BBcassette with a plurality of secondary capacity expansion interfacesamong the BBUs; and connecting the plurality of BBUs with the secondarycapacity expansion interfaces of the exchange BB cassette via therespective primary capacity expansion interfaces of BBUs to achieveinterconnection among the BBUs. Preferably, the method further includes:the exchange BB cassette setting up an electrical connection of theactive/standby switchover control signal between the master BBU and thestandby BBU according to the operation state of every BBU.

Preferably, the RFU is a radio remote unit (RRU), and the methodincludes: connecting the BBU and the RRU via a transmission mediums.

Preferably, the transmission mediums are optical fibers or electricalcables.

Preferably, the RFU is a near-end RFU.

Preferably, the BBUs are connected with each other via transmissionmediums. The transmission mediums are optical fibers or electricalcables.

A base band unit (BBU) includes:

a Main Processing & Timing unit, for controlling a base station,exchanging signals and traffic data among the units in the base stationand providing clock signals;

a base band signal processing unit, for processing symbol-level andchip-level digital signals in physical layer;

a transmission unit, which is connected with a base station controllerfor intercommunicating data information between the base station and thebase station controller; and

an interface unit for intercommunicating with external data information,intercommunicating digital base band signals with the base band signalprocessing unit, and intercommunicating master control information withthe Main Processing & Timing unit;

wherein the interface unit including one or a plurality of primary baseband RF interface(s) for connecting with the RFU and transmittinguplink/downlink base band data and master controller state informationwith the RFU; a power supply interface for connecting with an externalpower supply; and a debugging interface for managing and maintaining thebase station; and

the Main Processing & Timing unit, the base band signal processing unit,the transmission unit and the interface unit are integrated.

Preferably, the primary base band RF interface is a high speed digitalinterface. The debugging interface is a serial port and/or a networkport. The interface unit further includes an identification interfacefor marking the type of the base station and the position of the BBU,and the identification interface is a DIP switch and/or a cableidentification interface. The reset interface is a button or a switch.The power supply interface further includes a warning bus interface forconnecting with equipment with RS485 port. The interface unit mayfurther includes: a capacity expansion interface for transmitting clocksynchronous signals, base band information, transmission information andmaster control information among BBUs to achieve interconnection anddata sharing among BBUs.

Preferably, the interface unit further includes at least one of: a resetinterface for resetting the base station; an identification interfacefor marking the type of the base station and the position of the BBU; apower supply switches for controlling power on and power off for itself;a test interface for connecting with external test equipments; a signalinput interface for receiving external clock signals; a Dry Contactinput interface for expanding input Dry Contact functions of the basestation; an electrostatic discharge (ESD) connector; and a protectground (PGND) terminal.

Preferably, the capacity expansion interface includes one or a pluralityof capacity expansion interface(s) providing the active/standbyswitchover control signal.

Preferably, the signal input interface includes at least one of a signalinput interface for receiving GPS synchronous clock signals and a signalinput interface for receiving 2M synchronous clock signals.

Preferably, the test interface includes at least one of a 10M testinterface for outputting 10M test synchronous clock signals and atransmission time interval (TTI) test interface for outputting TTIsignals.

Preferably, the BBU is placed in a spare space of a standard cabinetwith a height higher than or equal to 1 U.

Preferably, the Main Processing & Timing unit, the base band signalprocessing unit, the transmission unit and the interface unit areintegrated on a single board.

In view of the above technical solutions, in the distributed basestation system in accordance with embodiments of the present invention,the base band part is separated from the RF part. The base band unit(BBU) consisting of the base band part and the RF unit (RFU) consistingof the RF part are connected to each other via base band RF interfaces.Base band units are connected to each other via capacity expansioninterfaces to achieve capacity expansion in many flexible ways. In thismanner, the distributed base station system should take up smallerfloorage, lower the operational cost and simultaneously enhance theoperational reliability of the base station system.

On the basis of separated arrangement of the base band unit and the RFunit, the base band unit in accordance with embodiments of the presentinvention is further divided to several called base band capacity unitswhich have basic capacity according to the capacity. The basic base bandcapacity unit may be separated to each other so that each of the basicbase band capacity unit can support the minimum configuration of basestation capacity respectively, and the BBU can support macro basestation capacity while combining a plurality of basic base band capacityunit together. According to the present invention, all the units in theBBU, including the transmission unit, the Main Processing & Timing unit,the base band signal processor unit and the interface unit, for example,are integrated on a single board which is 1 U high or even lower than 1U. Then place the single board in an independent BBU box, thus reducingthe size and weight of the BBU. Therefore, according to the actualneeds, the BBU in the present invention can be installed freely in astandard cabinet with space being 19-inch wide and 1 U or higher than 1U, in macro base station transmission device cabin or in othernon-standard installation spaces. And distributed installation of theplurality of BBUs can be achieved with cable connection. That means thatany cabinet may house the BBU in accordance with embodiments of thepresent invention as long as the cabinet has 1 U high spare space,thereby more flexible, more practical, and lower installation andservice cost. Difficulties to find new station sites and expensive rentfor station sites may be avoid, due to using the empty space of theexisting stations.

Additionally, in accordance with embodiments of the present invention,the base band RF interface for connecting the BBU to the RFU and thecapacity expansion interface for achieving the fully-connected topologyof the BBU are set in the interface unit of the BBU. Through base bandRF interfaces, BBUs and RFUs can accomplish data intercommunication andachieve a plurality of networking modes for the base station, such as aring networking, a star networking, and a chain networking; throughcapacity expansion interfaces, BBUs can achieve self-cascading and BBUbackup. Thus, it not only solves small capacity of mini BBU, and ensurestimely expansion of the BBU capacity according to actual applicationneeds, but also enhances flexibility for the BBU capacity expansion andnew business features expansion, and lowers cost as well. Meanwhile,setting master and standby BBUs also can improve operational reliabilityof the base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the structure of a basestation in a mobile communication system;

FIG. 2 is a schematic diagram illustrating a network structure of adistributed base station system in accordance with a preferredembodiment of the present invention;

FIG. 3 is a schematic diagram illustrating a BBU composition structureof a distributed base station system in accordance with a preferredembodiment of the present invention;

FIG. 4 is a schematic diagram illustrating a BBU interface in accordancewith a preferred embodiment of the present invention;

FIG. 5 is a schematic diagram illustrating the connection of a BBUcapacity expansion interface in accordance with a preferred embodimentof the present invention;

FIG. 6 is a schematic diagram illustrating the connection of a BBU baseband RF interface in accordance with a preferred embodiment of thepresent invention;

FIG. 7(a) is a schematic diagram illustrating a star network of BBU andRRU in accordance with a preferred embodiment of the present invention;

FIG. 7(b) is a schematic diagram illustrating a ring network of BBU andRRU in accordance with a preferred embodiment of the present invention;

FIG. 7(c) is a schematic diagram illustrating a chain network of BBU andRRU in accordance with a preferred embodiment of the present invention;

FIG. 7(d) is a schematic diagram illustrating a composition network ofBBU and RRU in accordance with a preferred embodiment of the presentinvention;

FIG. 8 (a) is a schematic diagram illustrating a first embodiment ofnetwork structure of BBU and RRU in the present invention;

FIG. 8 (b) is a schematic diagram illustrating a second embodiment ofnetwork structure of BBU and RRU in the present invention;

FIG. 8 (c) is a schematic diagram illustrating a third embodiment ofnetwork structure of BBU and RRU in the present invention;

FIG. 8 (d) is a schematic diagram illustrating a fourth embodiment ofnetwork structure of BBU and RRU in the present invention;

FIG. 8 (e) is a schematic diagram illustrating a fifth embodiment ofnetwork structure of BBU and RRU in the present invention;

FIG. 8 (f) is a schematic diagram illustrating a sixth embodiment ofnetwork structure of BBU and RRU in the present invention;

FIG. 9 is a schematic diagram illustrating a ring network of a pluralityof BBUs in accordance with a preferred embodiment of the presentinvention;

FIG. 10 is a schematic diagram illustrating a fully-connected topologyof a plurality of BBU in accordance with a preferred embodiment of thepresent invention; and

FIG. 11 is a schematic diagram illustrating another fully-connectedtopology of a plurality of BBU in accordance with another preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the base station, according to preferred embodiments of the presentinvention, the base band part is separated from the RF part torespectively form a base band unit and an RF unit, and base band RFinterfaces are configured on the RFU for interconnecting with the BBUand transmitting data information, thereby forming a distributed basestation system. Based on the separation of the BBU and the RFU, thecapacity of BBU is further divided. Each of the BBU may be arrangedindependently, so that each BBU can support a minimum configuration anda plurality of BBUs in combination can support the capacity as a macrobase station. In accordance with the embodiments of the presentinvention, the transmission unit, the master controller & clocksynchronous unit, the baseband signal processing unit and the interfaceunit are highly integrated in the BBU, e.g. are integrated on a singleboard, and the board is put in a small BBU cassette to form anon-the-spot replaceable unit. Through capacity expansion interfaces andbase band RF interfaces provided by the BBU interface unit, networkingand capacity expansion among BBUs and among BBUs and RFUs in flexibleand convenient ways may be achieved, backup functions based on aplurality of BBUs also may be achieved. In this way, the operationalreliability of the base station may be enhanced and the base band unitbackup cost in traditional base stations may be lowered.

The BBU in the distributed base station system and the networkingmethods in accordance with the embodiments of the present invention maybe applied to a plurality of mobile communication modes, such as WCDMA,CDMA2000, TD-SCDMA, and GSM, and also may be applied to a wide bandwireless access (WBA). The technical solution of the present inventionis explained in detail as follows by taking the WCDMA system as anexample.

The technical solution of the present invention will be described indetail hereinafter with reference to accompanying drawings and preferredembodiments.

It is noted that the RFU in the embodiments of the present invention,used for converting signals between RF signals and base band signals andtransmitting RF signals, includes an RF signal processing unit, a poweramplifier unit and a duplexer. The RFU may be either a near-end RFU, ora radio remote unit (RRU) connected with the BBU via such transmissionmedium as optical fibers or electrical cables. The near-end RFU and theRRU both have base band RF interfaces for interconnecting with BBUs,other RFUs and other RRUs. The base band RF interfaces may be high-speeddigital interfaces, common public radio interfaces (CPRI), otherstandard interfaces, or self-defined interfaces. In the followingembodiments, the RFU adopts the RRU to forms a mixed networking mode. Inactual applications, the RFU may be a near-end RFU, or a combination ofa near-end RFU and an RRU to form a mixed networking mode.

FIG. 2 is a schematic diagram illustrating a network structure of adistributed base station system in the preferred embodiment of thepresent invention. As shown in FIG. 2, the separated BBU and RFU may benetworked with their respective interfaces in flexible ways. The RFU maybe a near-end RFU or an RRU. FIG. 2 does not indicate the specificcapacity expansion interconnection methods of the BBU. In actualapplications, interconnection of BBUs illustrated in FIG. 2 may beimplemented by directly connecting BBUs via cables or optical fibers toform various network topological structures, or by connecting aplurality of BBUs via additional exchange BB cassettes to form variousnetwork topological structures, such as a star network, a chain network,a ring network and so on. The network may be composed in many flexibleways, which will be explained in the following description in detail.The networking modes between RFUs and BBUs in FIG. 2 are only anexemplary description. In actual applications, the networking methodsare not limited to these modes, which will be explained in detail in thefollowing implementation ways. In FIG. 2, the BBUs are connected withone or a plurality of near-end RFU(s) or RRU(s) via base band RFinterfaces. Similarly, a plurality of near-end RFUs or RRUs can formvarious network topological structures with their own interconnectioninterfaces, which are not indicated in FIG. 2, and the specificnetworking modes will be supplied in the following embodiments. In theembodiments of the present invention, both BBUs and the RFUs include twoor more than two units.

FIG. 3 is a schematic diagram illustrating a BBU composition structureof the distributed base station system in the preferred embodiment ofthe present invention. In FIG. 3, the main processing unit and the clockunit are collectively called the Main Processing & Timing unit. As shownin FIG. 3, the BBU of the preferred embodiment includes the transmissionunit, the Main Processing & Timing unit, the base band signal processingunit, and the interface unit. All the units are integrated on a singleboard or in an on-the-spot replaceable unit, which is placed in anindependent BBU cassette. The BBU cassette may be 1 U high so that inactual applications, according to actual needs, the BBU cassette may beinstalled in a standard cabinet, in a macro base station transmissiondevice cabin with an installation space of 19 inches wide and 1 U ormore high, or in any other non-standard installation space in flexibleways. The height of the BBU cassette may be changed in flexible waysaccording to actual needs, and dispersed installation of a plurality ofBBUs may be achieved via cables. In the above, 1 U is a measurement unitof thickness or height, and 1 U=1.75 inches=44.5 mm.

In FIG. 3, the transmission unit is connected with an RNC via an Iubinterface to accomplish data information intercommunication between BBUsand the RNC. In this case, if the preferred embodiment of the presentinvention is applied to other communication systems, the transmissionunit is connected with the BSC of the corresponding mobile communicationsystem via standard interfaces in the applied mobile communicationsystem. The Main Processing & Timing unit serves to accomplish basestation control functions and signaling and traffic data exchangecontrol among the units in the base station, and simultaneously providea clock reference to the BBU or the capacity-expanded BBU according toconfiguration needs. The base band signal processing unit serves toaccomplish the processing of symbol-level and chip-level digital signalsin physical layer, and intercommunicate digital base band signals withIF signal processing units. The interface unit serves to provide variousinterfaces to support intercommunication between BBUs and external data,e.g., connecting and networking with RRUs, expanding capacity of BBUs,debugging the base station, resetting the base station, identifying thetype of the base station and the position of the installation slot,intercommunicating data between BBUs and the RNC, various testing andinputting synchronous clocks. As shown in FIG. 4, the interface unitincludes the following units.

A power supply interface serves to connect with an external DC/AC powersupply to supply operation power for the base station.

A debugging interface provides interfaces as serial ports and networkports to achieve management and maintenance of the base station byexternal equipments or service personnel.

An identification interface serves to mark the type of the base stationin the base station system and mark the position of the slot where theBBU cassette is located. Based on input messages from the identificationinterface, the main processing unit of the BBU should identify the typeof the base station and the position of the present slot where the BBUcassette is located. Different positions of slots correspond todifferent preset slot position labels, and different preset slotposition labels serve to mark operation states of BBUs, e.g., the masterBBU that works in an active state, the standby BBU that works in astandby state, or the slave BBU that works in a slave state. Theidentification interface may use DIP switches or ID interfaces of cablesto achieve the identification function. In a network of the base stationsystem, different distributive ways of BBUs correspond to differenttypes of base stations. For example, BBUs interconnected with each otherare located at the same base station site or at different base stationsites corresponding to different bases station types.

The BBU that works as a master BBU can configure slave BBUs or standbyBBUs according to the preset configuration circumstance, e.g. assignsone or all slave BBU(s) to process transmission data, and assigns acertain slave BBU to process specified subscriber channels; orconfigures a certain BBU that takes part in networking to process thedata of a specified RRU.

The reset interface is a reset button/switch and serves to reset thebase station. When the reset button/switch is pressed, the mainprocessing unit receives a reset signal and reboots the system.

One or a plurality of base band RF interface(s), with each of theinterfaces connected with one RRU, serve(s) to receive the uplink baseband data transmitted by the RRU, and transmit downlink base band datafrom the BBU to the RRU. Base band RF interfaces may be CPRI, otherstandards interfaces, or self-defined interfaces. BBUs and the RRUs areconnected via the base band RF interfaces by such transmission mediumsas optical fibers or electrical cables. The base band RF interfaces alsomay be directly connected with near-end RFUs to form a mixed typenetwork including local RFs and radio remote units.

The transmission interface, which serves to connect the RNC to the BBUto achieve base station data intercommunication between the BBU and theRNC, supports a plurality of such transmission interfaces as E1/T1, andrecovers a circuit clock as the work clock of the BBU from a pluralityof such interfaces code streams as E1/T1 code stream, E3/T3 code stream,and STM-1 code stream. When the transmission interface is used as ATMinterface, it can accomplish mapping of a plurality of transmissioninterfaces from ATM cell to E1/T1. The transmission interface is notlimited to an ATM interface, it also may be an interface that conformsto other protocols, such as IP.

The warning bus interface serves to connect equipment including RS485interface and performs data collection functions. For example, thewarning bus interface may be connected with an intelligent power supplyto monitor operation state of the intelligent power supply, and theinterface may be built in the power supply interface. The warning businterface may be expanded by the existing interface chips. The interfaceexpansion may include commonly known expansion methods in the prior art,which will not be further described here.

The Dry Contact input interface serves to expand input Dry Contactfunctions of the base station and performs warning test of the DryContact. The expansion of the Dry Contact input interface may includecommonly known expansion methods in the prior art, which will not befurther described here.

The power supply switch serves to control power on and power off of theBBU.

The test interface includes a 10M test interface for outputting 10M testsynchronous clock signals to facilitate connection with relevant testinstruments and includes a transmission time interval (TTI) testinterface for output of TTI signals to facilitate test of RF 141protocol.

The signal input interface includes a GPS signal input interface forreceiving GPS synchronous clock signals; a Bits signal input interfacefor receiving 2M synchronous clock signals. It is noted that the BBU maysimultaneously have the GPS signal input interface and the Bits signalinput interface, or have at least one of the interfaces according toactual needs.

The Capacity expansion interface includes a high speed digitalinterface, a clock synchronous interface, and an active/standbyswitchover control interface. Each capacity expansion interface isconnected with a BBU for interconnecting among the BBUs to expand BBUcapacity, achieving clock synchronization among the interconnected BBUs,and transferring such information as base band information, transmissioninformation and master controller information among the interconnectedBBUs. The base band information includes base band IQ data, functioncontrol data, and so on. The transmission information is the relevantinformation from the RNC while the master controller information is thecontrol information from the main processing unit.

The electrostatic discharge (ESD) connector serves to connect an ESDwrist strap, and the protect ground (PGND) terminal serves to connect aprotective earth wire.

In addition, in order to display the BBU operation states, the BBUinterface unit in accordance with the embodiments of the presentinvention also provides state indicators for indicating whether thepower supply is normal or not, the interface of the BBU is normal ornot, and etc. The number of the state indicators depends on actualneeds.

In actual applications, each of the above-mentioned interfacescorresponds to an interface terminal on the BBU cassette panel and theinstallation positions of all the interface terminals may be arrangedrandomly on the panel.

Among all the above-mentioned interfaces, the capacity expansioninterface and the base band RF interface are important for capacityexpansion and networking of the BBU. FIG. 5 is a schematic diagramillustrating the connection of the BBU capacity expansion interface inaccordance with the embodiments of the present invention. As shown inFIG. 5, when two BBUs are interconnected, on the assumption that the BBUwith a capacity expansion interface is BBU1 and the BBU connected to theBBU1 via the capacity expansion interface is BBU2, then the BBU1 and theBBU2 share some information as the master control information of themain processing unit, the transmission information of the transmissionunit, the base band information of the base band signal processing unitand the master control information of the main processing unit via atransmission processing unit and a reception processing unit. That is,the BBU1 transmits the master control information, the transmissioninformation, or the base band information to the BBU2 via thetransmission processing unit and the BBU1 receives the master controlstate report information, the transmission information, or the base bandinformation from the BBU2 via the reception processing unit. Thecapacity expansion interface is connected with the clock unit to achieveclock synchronous functions. The transmission/reception processing unitis connected with the capacity expansion interface to accomplish signalconversion functions mainly, such as conversion between signalprotocols, conversion between electrical signals and optical signals,etc.

Additionally, if there is no active/standby switchover control signalsbetween the main processing unit and the capacity expansion interface,on the assumption that the BBU1 with the capacity expansion interface isset as a master BBU by using a DIP switch, while the BBU2 is set as aslave BBU by using a DIP switch, the BBU1 and the BBU2 are connected viathe capacity expansion interface and form a master-slave mode, in whichBBU1 and BBU2 are both in operation state and work by sharinginformation. In this manner, capacity of the BBU is increased. In thiscase, the capacity expansion interface with no active/standby switchovercontrol signals may be called an Eib capacity expansion interface. TheEib interface serves to transmit base band information, transmissioninformation, master control information and clock signals. In actualapplications, there may be single or a plurality of Eib interface(s).

If there exists active/standby switchover control signal between themain processing unit and the capacity expansion interface, as shown inFIG. 5, on the assumption that the BBU1 with the capacity expansioninterface is set as a master BBU by using the DIP switch, while the BBU2is set as a standby BBU by using the DIP switch, the BBU1 and the BBU2are connected with each other via the capacity expansion interface andform a master-standby mode. In normal cases, the BBU1 and the BBU2 workin load-share backup operation mode with data shared between them.Similar to the master-slave operation mode, the BBU2 operation statesare the same as the BBU1 except some functions. For example, thereference clock information is provided by the BBU1. When the mainprocessing unit of the BBU1 fails, the BBU1 degrades itself to standbystate automatically by the master-standby switchover control signal, andthe BBU2 upgrades to a master BBU when it detects the degradation ofBBU1 so as to promote operational reliability of the base station. Atthe same time, because the standby BBU is in hot backup operation state,the BBU capacity may be expanded simultaneously so as to achieve theobject of BBU capacity expansion. In this case, the capacity expansioninterface with active/standby switchover control signals may be calledan Eia capacity expansion interface, which serves to transmit base bandinformation, transmission information, master control information, clocksignals and active/standby switchover control signals. Compared to theEib interface, the Eia interface has one more kind of active/standbyswitchover control signal, while other signals are similar. In actualapplication, there may be single or a plurality of Eia interface(s).

A plurality of BBUs may be connected with each other via capacityexpansion interfaces by using optical fibers or electrical cables so asto achieve BBU capacity expansion conveniently.

The above-mentioned method to achieve data sharing among a plurality ofBBUs via capacity expansion interfaces is that every BBU taking part innetworking has a transmission unit which is connected to a logicalmodule via a special parallel transmission interface to achievetransmission data sharing among BBUs. The logical module is located inthe interface unit to achieve conversion between the ATM cell and thehigh speed data or between other cell and the high speed data. On theassumption that the BBU receiving uplink data from the RRU or downlinkdata from the RNC directly is a source BBU, and the BBU receiving theuplink/downlink data from the source BBU is a target BBU, so the actualmethod for data sharing is described as follows.

(1) For the downlink data, after receiving the data, the transmissionunit of the source BBU converts the received data into ATM cell andexchanges the ATM cell to the logical module of the source BBU via thespecial transmission interface according to the target BBU addresscarried in the data. The logical module of the source BBU converts theATM cell into high-speed data and transmits the high-speed data to thetarget BBU via the capacity expansion interface. The logical module ofthe target BBU receives the high-speed data via the capacity expansioninterface and converts the received high-speed data into ATM cell, andthen sends the ATM cell to the base band signal processing unit of thetarget BBU via the special transmission interface. The base band signalprocessing unit turns the received ATM cell into FP frames and processesthe frames with corresponding code modulation to get a base banddownlink data, and finally sends the base band downlink data to the RRUvia the base band RF interface between the target BBU and the RRU.

(2) For an uplink data, the RRU sends the uplink base band data to thecorresponding source BBU via the RF interface between the RRU and theBBU. After receiving the uplink base band data, based on the target BBUaddress carried in the uplink base band data, the logical module of thesource BBU sends the received data to the target BBU via the high-speeddata interface in the capacity expansion interface. The logical moduleof the target BBU receives the data via the capacity expansion interfaceand relays the data to the base band signal processing unit. The baseband signal processing unit demodulates and transcodes the base banddata, converts the transcoded data into ATM cell, and then sends the ATMcell to the transmission unit of the target BBU via the specialtransmission interface. The transmission unit processes the received ATMcell and gets the transmission uplink data, and finally sends thetransmission uplink data to the RNC via the transmission interfacebetween the target BBU and the RNC.

It should be noted that, the principles of data sharing, as abovementioned, are the same no matter if the source BBU and the target BBUhave a master-slave relationship or a master-standby relationship. Thedifference is in that the switchover function is available between themaster-standby BBUs but is not available between the master-slave BBUs.

FIG. 6 is a schematic diagram illustrating the connection of the BBUbase band RF interface in accordance with embodiments of the presentinvention. Compared with FIG. 5, it is shown in FIG. 6 that the baseband RF interface and the RRUs connected via the base band RF interfacetransmit base band information of the base band signal processing unitbetween them. That is, the BBU sends the base band information to theRRU via the transmission processing unit receives the base bandinformation from the RRU via the reception processing unit. Thetransmission/reception processing unit is connected with the base bandRF interface to accomplish such signal conversion functions as signalprotocol conversion, format conversion between electrical signals andoptical signals and etc. The RRUs are connected to each other via baseband RF interfaces by using transmission medium like optical fibers orelectrical cables so as to achieve the networking of the BBUs and theRRUs conveniently. Similarly, the base band RF interface may beconnected to a near-end RFU to accomplish the same functions as well.Networking of the base station system may simultaneously include thenear-end RFUs and the RRUs according to actual needs to form a mixedbase station system.

The capacity expansion interface of the BBU provided in accordance withthe embodiments of the present invention brings great convenience forthe BBU capacity expansion and the base station networking, lowers costand enhances operational reliability of the BBU. In the embodiment ofthe present invention, one or a plurality of BBU(s) and one or aplurality of RRU(s) may achieve various networking types, such as starnetwork, ring network, chain network or mixed network. In the followingnetworking schemes, the number of BBUs and RRUs is not limited tothereof. It may be planned according to the actual applicationconditions.

FIG. 7(a) is a schematic diagram illustrating star network with two BBUsand three RRUs in accordance with the embodiments of the presentinvention. As shown in FIG. 7(a), the BBU1 and the BBU2 may be connectedvia the Eia capacity expansion interface so that the BBU1 and the BBU2have a master-standby relationship, or may also be connected via the Eibcapacity expansion interface so that the BBU1 and the BBU2 have amaster-slave relationship. The BBUs and the RRUs are connected via baseband RF interfaces. Each BBU may provide a plurality of base band RFinterfaces for RRUs. For example, the BBU1 and the BBU2 in FIG. 7(a)have three base band RF interfaces respectively. Thus the BBU1 and theBBU2 may be connected with at least three RRUs respectively.

FIG. 7 (b) is a schematic diagram illustrating a ring network with twoBBUs and four RRUs in accordance with the embodiments of the presentinvention. Similarly, the BBU1 and the BBU2 form a network withmaster-slave relationship by being connected via the Eib capacityexpansion interface. The BBU1 is connected with one RRU via the baseband RF interface, and the BBU2 is connected with another RRU via thebase band RF interface. The RRUs are consecutively interconnected viabase band RF interfaces. In this way, the two BBUs and four RRUs form aring network. In this case, the network capacity is the sum of the twoBBUs' capacities. If the BBU1 and the BBU2 are connected via the Eiacapacity expansion interface and have a master-standby relationship, allthe functions and capacity of the network formed with Eib interface maybe achieved, furthermore, backup function is also provided for thenetwork so as to enhance operational reliability of the whole basestation.

FIG. 7 (c) is a schematic diagram illustrating a chain network with oneBBU and three RRUs in accordance with the embodiments of the presentinvention. The base band RF interface of the BBU is connected with acertain RRU, The RRUs are consecutively connected via correspondinginterfaces. In this manner, one BBU and three RRUs form a chain network.In this case, the Eib capacity expansion interface of the BBU may beused to expand the BBU capacity or the Eia capacity expansion interfaceof the BBU may be used for the BBU backup.

FIG. 7 (d) is a schematic diagram illustrating a mixed network with twoBBUs and six RRUs in accordance with the embodiments of the presentinvention. As shown in FIG. 7 (d), there are two RRUs in each sector,and each RRU is connected with BBU respectively. With regard to eachsector, RRUs and BBUs in each sector form a ring network supportingdouble-RRU configuration. With regard to a plurality of sectors, starnetwork connection is adopted among sectors. Therefore, the networkingmode illustrated in FIG. 7 (d) is a method for achieving mixed network.The BBU1 and the BBU2 may have a master-standby relationship or amaster-slave relationship.

In the following, a star networking mode formed by the RRUs and the BBUseach of which respectively has two capacity expansion interfaces andthree base band RF interfaces, is taken as an example for a specificdescription of the scheme to achieve the capacity expansion of BBUs withRRUs. Herein, it is assumed that one of the two capacity expansioninterfaces is the Eia interface and the other is the Eib interface.

FIG. 8 (a) is a schematic diagram illustrating the first embodiment ofthe network structure with one BBU and three RRUs. As shown in FIG. 8(a), one BBU and three RRUs are connected respectively via a base bandRF interface. Each of the RRUs belongs to a sector, and each of the RRUsadopts a networking configuration with single carrier wave. That is, thenetworking mode illustrated in FIG. 8 (a) supports networking of 3×1configuration, in which 3 refers to 3 sectors, and 1 means singlecarrier wave.

FIG. 8 (b) is a schematic diagram illustrating the second embodiment ofnetwork structure with two BBUs and three RRUs in the present invention.As shown in FIG. 8 (b), the BBU1 and the RRU2 are connected via an Eiacapacity expansion interface to form network with master-standbyrelationship. The BBU1 and the BBU2 are connected with three RRUsrespectively via three base band RF interfaces respectively, each of theRRUs belongs to a sector, and each of the RRUs adopts a networkingconfiguration with single carrier wave backup. That is, the networkingmode illustrated in FIG. 8 (b) supports networking of 3×1 configuration,in which 3 refers to 3 sectors, and 1 means single carrier wave. Supposethat the slot position label of the BBU1 is preset as a master BBUidentifier, and the slot position label of the BBU2 is preset as astandby BBU identifier, then, the operation principles of the networkingin FIG. 8 (b) are described as follows. After accomplishing thenetworking as illustrated in FIG. 8 (b), in normal cases, the BBU1 andthe BBU2 are in independent operation state. The BBU2 is in hot backupoperation state, and the main processing unit of the BBU1 controllingthe whole system, while the BBU1 and the BBU2 share data through thecapacity expansion interfaces. The specific ways to achieve capacityexpansion interfaces and to achieve data sharing have been introduced inthe above, so no more description is provided here. When the mainprocessing unit of the BBU1 fails, the BBU1 reboots automatically, andsimultaneously sends an active/standby switchover control signal to theBBU2. The BBU2 works as the master BBU, and the main processing unit ofthe BBU2 controls the whole system, while the BBU1 is degraded to thestandby BBU for operation. The operation states of each BBU will bereported to the RNC after failure occurs so as to facilitate personnelin taking opportunity measures.

It should be noted that the active/standby switchover function occursonly when the main processing unit fails. When the other units, such asthe base band signal processing unit, or the base band RF interface, orthe capacity expansion interface fails, the active/standby switchoverfunction is not generally performed. For example, when the base bandsignal processing unit or the base band RF interface is out of order andaffects configuration conditions of the present network, theactive/standby switchover function can do no help at all. In this case,even if the BBU1 is degraded to the standby BBU, communication betweenthe BBU1 and the RRU has been interrupted, and normal operation can notbe maintained any longer. Therefore, in such a case, what is needed onlyis that the BBU reports the failure to the RNC.

FIG. 8 (c) is a schematic diagram illustrating the third embodiment ofnetwork structure with two BBUs and three RRUs. As shown in FIG. 8 (b),the BBU1 and the RRU2 are connected via an Eib capacity expansioninterface and form a network with master-slave relationship. The BBU1are connected with three RRUs respectively via three base band RFinterfaces. Each of the RRUs belongs to a sector, and each of the RRUsadopts a network configuration with two-carrier wave. That is, thenetworking mode illustrated in FIG. 8 (c) supports networking of 3×2configuration, in which, 3 refers to 3 sectors, and 2 means 2 carrierwaves. Since the BBU1 and the BBU2 have a master-slave relationship, theBBU uplink/downlink data capacity is increased to twice of that when asingle BBU is used.

The operation principles of networking illustrated in FIG. 8 (c) arecompletely the same as those in FIG. 8 (b). The difference between themis in that in FIG. 8 (c), failure of the BBU1 is only reported to theRNC with no backup function, no matter what kind of failure it is.

On the basis of the above mentioned BBU master-standby relationship andBBU master-slave relationship for expanding capacity, the BBUs inaccordance with the embodiments of the present invention may achievemany flexible ways for expanding capacity by using various networkingmodes. Several ways are listed in the following with reference to theaccompanying drawings.

FIG. 8 (d) is a schematic diagram illustrating the fourth embodiment ofnetwork structure with four BBUs and six RRUs. As shown in FIG. 8 (d),the BBU1 and the BBU2 are connected via an Eia capacity expansioninterface to form network with master-standby relationship. The six RRUsare divided into groups with two RRUs belonging to each group to form amain-and-diversity mode. The BBU1 is connected with three main RRUs viathree base band RF interfaces respectively, while the BBU2 is connectedwith three diversity RRUs via three base band RF interfacesrespectively. Two RRUs belong to one sector, and this networking modesupports three sectors, in which, every RRU adopts a networkconfiguration with two-carrier wave backup. That is, the networking modeillustrated in FIG. 8 (d) supports backup networking of 3×2 transmitdiversity configuration, in which, 3 refers to 3 sectors and 2 means 2carrier waves.

If the BBU1 and the BBU3 are connected via the Eib capacity expansioninterface to form a network with master-slave relationship, the BBU2 andthe BBU4 are connected via the Eib capacity expansion interface to forma network with master-slave relationship, the networking mode supportsthree sectors. In which, every RRU adopts a network configuration withtwo-carrier wave backup. That is, the networking mode supports backupnetworking of 3×2 transmit diversity configuration, in which, 3 refersto 3 sectors and 2 means 2 carrier waves. Herein, Eia capacity expansioninterfaces may be used between the BBU1 and the BBU3 and between theBBU2 and the BBU4 to form a network with master-standby relationship. Insuch conditions, the main processing unit of the BBU1 or the BBU2shields the active/standby switchover control signal sent to the BBU3 orthe BBU4, where the shielding means that the main processing unit setsthe active/standby switchover control signal invalid.

FIG. 8 (e) is a schematic diagram illustrating the fifth embodiment ofnetwork structure with three BBUs and six RRUs. As shown in FIG. 8 (e),the BBU1 and the BBU2 are connected via an Eia capacity expansioninterface to form a network with master-standby relationship, the BBU1and the BBU3 are connected via an Eib capacity expansion interface toform a network with master-slave relationship, and the BBU2 and the BBU3are connected via an Eib capacity expansion interface to form a networkwith master-slave relationship. Six RRUs are divided into groups withtwo RRUs belonging to each group. The BBU1 is connected to one RRU ofevery group respectively via the base band RF interface. The BBU2 isconnected to the other RRU of every group respectively via the base bandRF interface. Two RRUs belong to one sector, and this networking modesupports three sectors, in which every group of RRUs adopts a networkconfiguration with three-carrier wave backup. That is, the networkingmode illustrated in FIG. 8 (e) supports the backup networking of 3×3configuration, in which, the first 3 refers to 3 sectors, and the second3 means 3 carrier waves.

FIG. 8 (f) is a schematic diagram illustrating the sixth embodiment ofnetwork structure with four BBUs and six RRUs. As shown in FIG. 8 (f),the BBU1 and the BBU2 are connected via an Eia capacity expansioninterface to form a network with master-standby relationship. The BBU1and the BBU3 are connected via an Eib capacity expansion interface toform a network with master-slave relationship. The BBU2 and the BBU4 areconnected via an Eib capacity expansion interface to form a network withmaster-slave relationship. The BBU3 and the BBU4 are connected via theEia capacity expansion interface to form a network with master-slaverelationship. It should be noted that the active/standby switchovercontrol signal between the BBU3 and the BBU4 is shielded when the BBU3and the BBU4 are connected via an Eia capacity expansion interface. Thesix RRUs are divided into groups with two RRUs belonging to each groupto form a main-and-diversity mode. The BBU1 is connected with the threemain RRUs respectively via three base band RF interfaces, while the BBU2is connected with the three diversity RRUs via three base band RFinterfaces respectively. The networking mode supports three sectors, inwhich, every RRU adopts a network configuration with four-carrier wavebackup. That is, the networking illustrated in FIG. 8 (f) supports thebackup networking of 3×4 transmit diversity configuration, in which, 3refers to 3 sectors, and 4 means 4 carrier waves.

With regards to BBUs only, there are different ways for expandingcapacity among a plurality of BBUs, which will be described in detailhereinafter with reference to the accompanying drawings.

FIG. 9 is a schematic diagram illustrating a ring network with four BBUsin accordance with the embodiment of the present invention. The BBU1 andthe BBU2 are connected via an Eia capacity expansion interface to form anetwork with master-standby relationship. The BBU1 and the BBU3, theBBU2 and the BBU4 are respectively connected via Eib capacity expansioninterfaces. The BBU3 and the BBU4 are connected via an Eia capacityexpansion interface. In this way, the BBU1 and the BBU3 form a networkwith master-slave relationship, the BBU2 and the BBU4 form a networkwith master-slave relationship, and the BBU3 and the BBU4 form a networkwith slave relationship. Suppose that every capacity expansion interfaceof the BBU in FIG. 9 includes one Eia capacity expansion interface andone Eib capacity expansion interface, the master-slave relationshipbetween the BBU3 and the BBU4 may be achieved via the Eia interface.Only the main processing unit of the BBU3 shields the active/standbyswitchover control signal that is sent to the capacity expansioninterface connected with the BBU4. The master-slave relationship betweenthe BBU3 and the BBU4 can also be achieved with an additional Eibinterface added between the BBU3 and the BBU4.

In the interconnection scheme of BBUs in FIG. 9, every BBU may beconnected via respective capacity expansion interfaces by using thetransmission mediums like optical fires or electrical cables, and thecapacity of base station system increases with the increase of BBUsquantity. This ring networking mode can achieve data sharing among BBUswith a small number of capacity expansion interfaces, and providecircuit protective functions due to the inherent ability of ringnetwork.

FIG. 10 is a schematic diagram illustrating a fully-connected topologyof a plurality of BBUs in accordance with the embodiment of the presentinvention. Every BBU in FIG. 10 should respectively have at least oneEia interface and a plurality of Eib interfaces. The BBU1 and the BBU2are connected via Eia capacity expansion interfaces to form a networkwith master-backup relationship. The BBU3 and the BBU4 are connected viathe Eia capacity expansion interface that supports the active/standbyswitchover function but with the active/standby switchover functionshielded, so that it only achieves information sharing between the BBU3and the BBU4 but has no master-backup switchover function. The BBU1 andthe BBU3, the BBU2 and the BBU4, the BBU1 and the BBU4 as well as theBBU2 and the BBU3 are all connected via Eib capacity expansioninterfaces. It may be seen that every BBU in FIG. 9 should have at leastone Eia interface and two or more Eib interfaces.

In the fully-connected topology of BBUs in FIG. 10, every BBU may beconnected via respective capacity expansion interfaces by using thetransmission mediums like optical fires or electrical cables, and thecapacity of base station system increases with the increase of BBUquantity.

FIG. 11 is a schematic diagram illustrating another fully-connectedtopology of a plurality of BBUs in accordance with the embodiment of thepresent invention. In FIG. 11, one exchange BB cassette is added amongfour BBUs, and it helps achieving interconnection among BBUs. Theexchange BB cassette provides a plurality of capacity expansioninterfaces for connecting with BBU capacity expansion interfaces,identifies the nature of the BBU according to the slot position label ofeach BBU, and builds up electrical connection for active/standbyswitchover control signals between the master BBU and the backup BBU. Itis not necessary to build up electrical connection for active/standbyswitchover control signals between the master BBU and slave BBUs, thestandby BBU and the slave BBUs, or among slave BBUs. Data among theseBBUs is transmitted by the exchange BB cassette, which transmits data tothe corresponding BBU according to the address of the target BBU carriedin the data.

In the fully-connected topology with four BBUs in FIG. 11, every BBU maybe connected via respective capacity expansion interfaces by using thetransmission mediums like optical fires or electrical cables. Thecapacity of the base station system may increase with the increase ofBBU quantity. The exchanging BB cassette exchanges data among the BBUsto achieve point-to-point or point-to-multipoint informationtransmission. It is obvious that the exchanging BB cassette can help toreduce the number of BBU capacity expansion interfaces dramatically andlower the cost of the BBU when network composition becomes morecomplicated with increased number of BBUs.

In the BBU in accordance with the embodiment of the present invention,based on the capacity of base band part, the base band part of the basestation is divided into a plurality of small capacity base band unitsthat may be expanded in flexible ways. Due to its small capacity, a baseband unit may be made very compactly in size so that it may be placed ina space-limited location to achieve the object of “to be invisible”.Simultaneously, interconnection among a plurality of BBUs may beachieved with BBU capacity expansion interfaces, so as to help thesystem achieve the capacity of macro base station. Compared with themacro base station, the BBU in accordance with the embodiment of thepresent invention integrates the master control function, the base bandfunction and the transmission function, and places all the interfaces ofthe master control function, the base band function and the transmissionfunction on a single box, thereby reducing the equipment size and weightand expanding application scope of the equipment. Compared with the ministation, the BBU in accordance with the embodiment of the presentinvention, not only integrates the master control function, the baseband function and the transmission function, but also providesinterfaces for interconnection and expansion, which can achieveexpansion and overlapping of the base band part to reach the capacity ofthe macro station, thereby further expanding application scope of themini station.

It may be seen from the technical solution provided by the presentinvention that the BBU in accordance with the embodiments of the presentinvention may be dispersedly installed by downsizing design. Mobilecommunication operators, as long as they already have base stationsites, can install BBUs in accordance with embodiments of the presentinvention directly in the remaining space of their outdoor macro basestations, or in the remaining space in the machine cabinets or frames oftheir indoor macro station machine rooms. They don't have to findadditional base station sites. Simultaneously, because of theminimization and dispersed installation of equipments, the mobilecommunication operators can dramatically shorten their networkconstruction time to achieve quick network construction.

The BBU cassette in accordance with the embodiments of the presentinvention is an independent device, which solves the problems ofcomplicated installation, high requirements on weight bearing and highinstallation cost aroused by big size of traditional base station andheavy weight, and avoids the disadvantages of mini/micro base station'sdifficulties in capacity expansion as well as the problems to upgradebase band signal processing unit and RFU.

In accordance with the embodiments of the present invention, every BBUprovides the transmission interface function, and a plurality of BBUsform distributed processing with their internal functional modules whenthey are interconnected, and can achieve networking in various modeswith RRUs or near-end RFUs via BBU base band RF interfaces. Every partof the whole system has protection mechanism and the system is of simplestructure and is easy to achieve backup with low backup cost, and it canwell meet telecommunication equipment's requirements on base station'sreliability in future.

In accordance with the embodiments of the present invention, equipmentsthat the operators have already purchased and base station sites thatthe operators have already obtained may be used to reduce their futureinvestment with further exploitation of the existing facilities'efficiency. Mobile communication operators can achieve multi-mode basestations at their existing base station sites and on their existing basestation equipment, so that the operators can make full use of theirexisting investments and reduce repeated investments by utilization ofthe space in the existing equipment and the existing power supplies.

The distributed base stations disclosed in accordance with embodimentsof the present invention may be applied but not limited to WCDMAproducts, CDMA2000 products, GSM products and BWA products, and etc.

The foregoing are only preferred embodiments of the present inventionwhile the protection scope thereof is not limited to the abovedescription. Any change or substitution, within the technical scopedisclosed by the present invention, easily occurring to those skilled inthe art should be covered by the protection scope of the presentinvention. Therefore, the protective range of the present inventionshould be determined by the protective range of Claims.

1. A distributed base station system comprising: a base band unit (BBU),which comprises a Main Processing & Timing unit, a base band signalprocessing unit, a transmission unit, and an interface unit forproviding an interface for intercommunicating data with an externalunit, intercommunicating digital base band signals with the base bandsignal processing unit, and intercommunicating master controlinformation with the Main Processing & Timing unit; wherein theinterface unit comprises one or a plurality of primary base band RadioFrequency (RF) interface(s); and the interface unit being integratedwith the Main Processing & Timing unit, the base band signal processingunit and the transmission unit; and a Radio Frequency unit (RFU) whichcomprises a secondary base band RF interface thereon; wherein theprimary base band RF interface of the BBU is connected with thesecondary base band RF interface of the RFU, and the BBU transmitsuplink/downlink base band data and master controller state informationwith the RFU via the primary base band RF interface and the secondarybase band RF interface.
 2. The system according to claim 1, wherein theprimary base band RF interface and the secondary base band RF interfaceboth are high speed digital interfaces.
 3. The system according to claim1, wherein the base station system comprises a plurality of BBUs, andthe BBUs are interconnected with each other via wire cables or opticalfibers; the interface unit of each BBU comprises one or a plurality ofprimary capacity expansion interface(s) for transmitting synchronousclock signals, base band information, transmission information and themaster control information among BBUs, to achieve interconnection anddata sharing among BBUs.
 4. The system according to claim 3, wherein theprimary capacity expansion interface comprises a primary capacityexpansion interface that provides an active/standby switchover controlsignal.
 5. The system according to claim 3, wherein the interface unitfurther comprises an identification interface for marking the type ofthe base station and the position of the BBU.
 6. The system according toclaim 3, wherein the interface unit further comprises a Dry Contactinput interface for expanding the input Dry Contact functions of thebase station.
 7. The system according to claim 3, wherein the BBUscomprise a master BBU that works in an active state
 8. The systemaccording to claim 7, wherein the BBUs comprise a standby BBU that worksin a standby state.
 9. The system according to claim 8, wherein the RFUis connected with any one of the plurality of BBUs.
 10. The systemaccording to claim 7, wherein the BBUs comprise a slave BBU that worksin a slave state.
 11. The system according to claim 3, furthercomprising: an exchange BB cassette with a plurality of secondarycapacity expansion interfaces, and each BBU is connected with one of thesecondary capacity expansion interfaces on the exchange BB cassette viathe respective primary capacity expansion interface of the BBU.
 12. Thesystem according to claim 1, wherein the RFU is a radio remote unit(RRU).
 13. The system according to claim 12, wherein the RRU and the BBUare connected with each other via transmission mediums.
 14. The systemaccording to claim 1, wherein the RFU is a near-end RFU.
 15. The systemaccording to claim 1, wherein the BBU is placed in a spare space of astandard cabinet with a height higher than or equal to 1 U.
 16. A methodfor networking a distributed base station system, comprising: separatingthe base station system into a BBU and an RFU in dispersed arrangement,wherein the BBU comprises an integration of a base band signalprocessing unit, a transmission unit, a Main Processing & Timing unitand a interface unit; the interface unit of the BBU comprises a primarybase band RF interface, and the RFU comprises at least one secondarybase band RF interface; and connecting the BBU and the RFU through theprimary base band RF interface of the BBU and the secondary base band RFinterface of the RFU.
 17. The method according to claim 16, wherein thebase station system comprises a plurality of BBUs, and the interfaceunit of each BBU comprises a primary capacity expansion interface; themethod further comprising: setting an operation state of the BBU; andconnecting the BBUs with each other via the primary capacity expansioninterface on the interface unit thereof.
 18. The method according toclaim 16, wherein the base station system comprises a plurality of RFUs,each RFU comprises a plurality of base band RF interfaces; the methodfurther comprising: connecting a plurality of RFUs with each other viatheir respective secondary base band RF interfaces.
 19. The methodaccording to claim 17, wherein the base station system comprises twoBBUs and the step of setting the operation state of the BBU comprises:setting one of the BBUs as a master BBU that works in an active statewhile setting the other BBU as a standby BBU that works in a standbystate; and the step of connecting the BBUs to each other via the primarycapacity expansion interface comprises: connecting the master BBU to thestandby BBU via the primary capacity expansion interface that providesan active/standby switchover control signal.
 20. The method according toclaim 17, wherein the step of setting the operation state of BBUscomprises: setting any one of the plurality of BBUs as a master BBU thatworks in the active state, and setting the others as slave BBUs thatwork in slave states; and the step of connecting the BBUs to each othervia the primary capacity expansion interface comprises: connecting themaster BBU and slave BBUs via one or a plurality of primary capacityexpansion interface(s) providing no active/standby switchover controlsignal.
 21. The method according to claim 17, wherein the step ofsetting the operation state of the BBU comprises: setting any one of theplurality of BBUs as a master BBU that works in an active state, andsetting the others as slave BBUs that work in slave states; and the stepof connecting BBUs with each other via the capacity expansion interfacescomprises: connecting the master BBU with the slave BBUs via one or aplurality of primary capacity expansion interface(s) providing theactive/standby switchover control signal; and the Main Processing &Timing unit of the master BBU shielding the active/standby switchovercontrol signal.
 22. The method according to claim 20, wherein the stepof connecting BBUs with each other via the capacity expansion interfacescomprises: connecting the master BBU with each of the slave BBUs via oneor a plurality of primary capacity expansion interface(s) providingactive/standby switchover control signals; and the Main Processing &Timing unit of the master BBU shielding the active/standby switchovercontrol signal.
 23. The method according to claim 17, wherein the stepof setting the operation state of BBU comprises: setting anyone of the aplurality of BBUs as a master BBU that works in an active state, settinganother one of the plurality of BBUs as a standby BBU that works instandby state, and setting the others as slave BBUs working in slavestates, the master BBU and the standby BBU being not the same one; andwherein the step of connecting BBUs with each other via the primarycapacity expansion interfaces comprises: connecting the master BBU withthe standby BBU via the primary capacity expansion interface thatprovides the active/standby switchover control signal, and connectingthe standby BBU with the slave BBU via one or a plurality of primarycapacity expansion interface(s) providing no active/standby switchovercontrol signals.
 24. The method according to claim 17, wherein the stepof setting the operation state of BBUs comprises: setting any one of theplurality of BBUs as a master BBU that works in an active state, settinganother one of the plurality of BBUs as a standby BBU that works in astandby state, and setting the others as slave BBUs that work in slavestates, the master BBU and the standby BBU being not the same one; andwherein the step of connecting BBUs to each other via the primarycapacity expansion interfaces comprises: connecting the master BBU withthe standby BBU via the primary capacity expansion interface thatprovides the active/standby switchover control signal, and connectingthe standby BBU with the slave BBU via one or a plurality of primarycapacity expansion interface(s) providing the active/standby switchovercontrol signal, and the Main Processing & Timing unit in the standby BBUshielding the active/standby switchover control signal.
 25. The methodaccording to claim 23, wherein the step of connecting BBUs to each othervia capacity expansion interfaces comprises: connecting the standby BBUwith each slave BBU via one or a plurality of primary capacity expansioninterface(s) providing the active/standby switchover control signal withthe Main Processing & Timing unit in the standby BBU shielding theactive/standby switchover control signal.
 26. The method according toclaim 20, wherein the base station comprises a plurality of slave BBUs,and the plurality of slave BBUs are interconnected with each other viathe primary capacity expansion interfaces, the method further comprisingany one step of the following steps: interconnecting slave BBUs to eachother via primary capacity expansion interfaces that provide noactive/standby switchover control signal; interconnecting slave BBUs toeach other via primary capacity expansion interfaces that provide theactive/standby switchover control signal, meanwhile shielding theactive/standby switchover control signal by the Main Processing & Timingunit of at least one of the two interconnected slave BBUs.
 27. Themethod according to claim 21, wherein the base station comprises aplurality of slave BBUs, and the plurality of slave BBUs areinterconnected with each other via the primary capacity expansioninterfaces, the method further comprising any one step of the followingsteps: interconnecting the slave BBUs to each other via primary capacityexpansion interfaces that provide no active/standby switchover controlsignal; interconnecting slave BBUs to each other via primary capacityexpansion interfaces that provide the active/standby switchover controlsignal, and shielding the active/standby switchover control signal bythe Main Processing & Timing unit of at least one of the twointerconnected slave BBUs.
 28. The method according to claim 22, whereinthe base station comprises a plurality of slave BBUs, and the pluralityof slave BBUs are interconnected with each other via the primarycapacity expansion interfaces, the method further comprising any onestep of the following steps: interconnecting the slave BBUs to eachother via primary capacity expansion interfaces that provide noactive/standby switchover control signal; interconnecting the slave BBUsto each other via primary capacity expansion interfaces that provide theactive/standby switchover control signal, and shielding theactive/standby switchover control signal by the Main Processing & Timingunit of at least one of the two interconnected slave BBUs.
 29. Themethod according to claim 23, wherein the base station comprises aplurality of slave BBUs, and the plurality of slave BBUs areinterconnected with each other via the primary capacity expansioninterfaces, the method further comprising any one step of the followingsteps: interconnecting slave BBUs to each other via primary capacityexpansion interfaces that provide no active/standby switchover controlsignal; interconnecting slave BBUs to each other via primary capacityexpansion interfaces that provide the active/standby switchover controlsignal, and shielding the active/standby switchover control signal bythe Main Processing & Timing unit of at least one of the twointerconnected slave BBUs.
 30. The method according to claim 24, whereinthe base station comprises a plurality of slave BBUs, and the pluralityof slave BBUs are interconnected with each other via the primarycapacity expansion interfaces, the method further comprising any onestep of the following steps: interconnecting slave BBUs to each othervia primary capacity expansion interfaces that provide no active/standbyswitchover control signal; interconnecting slave BBUs to each other viaprimary capacity expansion interfaces that provide the active/standbyswitchover control signal, and shielding the active/standby switchovercontrol signal by the Main Processing & Timing unit of at least one ofthe two interconnected slave BBUs.
 31. The method according to claim 25,wherein the base station comprises a plurality of slave BBUs, and theplurality of slave BBUs are interconnected with each other via theprimary capacity expansion interfaces, the method further comprising anyone step of the following steps: interconnecting slave BBUs to eachother via primary capacity expansion interfaces that provide noactive/standby switchover control signal; interconnecting slave BBUs toeach other via primary capacity expansion interfaces that provide theactive/standby switchover control signal, and shielding theactive/standby switchover control signal by the Main Processing & Timingunit of at least one of the two interconnected slave BBUs.
 32. Themethod according to claim 17, further comprising: configuring anexchange BB cassette with a plurality of secondary capacity expansioninterfaces among the BBUs; and connecting the plurality of BBUs with thesecondary capacity expansion interfaces of the exchange BB cassette viathe respective primary capacity expansion interfaces of BBUs to achieveinterconnection among the BBUs.
 33. The method according to claim 32,further comprising: the exchange BB cassette setting up an electricalconnection of the active/standby switchover control signal between themaster BBU and the standby BBU according to the operation state of everyBBU.
 34. The method according to claim 16, wherein the RFU is a radioremote unit (RRU), and the method comprises: connecting the BBU and theRRU via transmission mediums.
 35. The method according to claim 34,wherein the transmission mediums are optical fibers or electricalcables.
 36. The method according to claim 16, wherein the RFU is anear-end RFU.
 37. The method according to claim 18, wherein the BBUs areconnected with each other via transmission mediums.
 38. The methodaccording to claim 37, wherein the transmission mediums are opticalfibers or electrical cables.
 39. A base band unit (BBU), comprising: aMain Processing & Timing unit, for controlling a base station,exchanging signals and traffic data among the units in the base stationand providing clock signals; a base band signal processing unit, forprocessing symbol-level and chip-level digital signals in physicallayer; a transmission unit, which is connected with a base stationcontroller for intercommunicating data information between the basestation and the base station controller; and an interface unit forintercommunicating with external data information, intercommunicatingdigital base band signals with the base band signal processing unit, andintercommunicating master control information with the Main Processing &Timing unit; wherein the interface unit comprising one or a plurality ofprimary base band RF interface(s) for connecting with the RFU andtransmitting uplink/downlink base band data and master controller stateinformation with the RFU; a power supply interface for connecting withan external power supply; and a debugging interface for managing andmaintaining the base station; and the Main Processing & Timing unit, thebase band signal processing unit, the transmission unit and theinterface unit are integrated.
 40. The Base band unit according to claim39, wherein the primary base band RF interface is a high speed digitalinterface.
 41. The Base band unit according to claim 39, wherein thedebugging interface is a serial port and/or a network port.
 42. The Baseband unit according to claim 39, wherein the interface unit furthercomprises an identification interface for marking the type of the basestation and the position of the BBU, and the identification interface isa DIP switch and/or a cable identification interface.
 43. The Base bandunit according to claim 39, wherein the reset interface is a button or aswitch.
 44. The Base band unit according to claim 39, wherein the powersupply interface further comprises a warning bus interface forconnecting with an equipment with RS485 port.
 45. The Base band unitaccording to claim 39, wherein the interface unit further comprises: acapacity expansion interface for transmitting clock synchronous signals,base band information, transmission information and master controlinformation among BBUs to achieve interconnection and data sharing amongBBUs.
 46. The Base band unit according to claim 45, wherein theinterface unit further comprises at least one of: a reset interface forresetting the base station; an identification interface for marking thetype of the base station and the position of the BBU; a power supplyswitches for controlling power on and power off for itself; a testinterface for connecting with external test equipments; a signal inputinterface for receiving external clock signals; a Dry Contact inputinterface for expanding input Dry Contact functions of the base station;an electrostatic discharge (ESD) connector; and a protect ground (PGND)terminal.
 47. The Base band unit according to claim 45, wherein thecapacity expansion interface comprises one or a plurality of capacityexpansion interface(s) providing the active/standby switchover controlsignal.
 48. The Base band unit according to claim 46, wherein the signalinput interface comprises at least one of a signal input interface forreceiving GPS synchronous clock signals and a signal input interface forreceiving 2M synchronous clock signals.
 49. The Base band unit accordingto claim 46, wherein the test interface comprises at least one of a 10Mtest interface for outputting 10M test synchronous clock signals and atransmission time interval (TTI) test interface for outputting TTIsignals.
 50. The Base band unit according to claim 39, wherein the BBUis placed in a spare space of a standard cabinet with a height higherthan or equal to 1 U.
 51. The Base band unit according to claim 39,wherein the Main Processing & Timing unit, the base band signalprocessing unit, the transmission unit and the interface unit areintegrated on a single board.